MAX9814

The MAX9814 is a low-cost, high-quality microphone amplifier with automatic gain control (AGC)and lownoise microphone bias. The device features a low-noise preamplifier, variable gain amplifier (VGA), output amplifier, microphone-bias-voltage generator and AGC control circuitry. A trilevel digital input of MAX9814 programs the output amplifier gain. An external resistive divider controls the AGC threshold and a single capacitor programs the attack/release times. A trilevel digital input programs the ratio of attack-to-release time. The low-noise preamplifier has a fixed 12dB gain, while the VGA gain automatically adjusts from 20dB to 0dB, depending on the output voltage and the AGC threshold. The output amplifier MAX9814 offers selectable gains of 8dB, 18dB, and 28dB. With no compression, the cascade of the amplifiers results in an overall gain of 40dB, 50dB, or 60dB. The hold time of the This device is specified over the -40°C to +85°C extended temperature range. AGC is fixed at 30ms. The low-noise microphone-biasvoltage generator can bias most electret microphones. The MAX9814 is available in the space-saving, 14-pin TDFN package.

The features of MAX9814 can be summarized as (1)automatic gain control (AGC); (2)three gain settings (40dB, 50dB, 60dB); (3)programmable attack time; (4)programmable attack and release ratio; (5)2.7V to 5.5V supply voltage range; (6)low input-referred noise density of 30nV/Hz; (7)low THD: 0.04% (typ); (8)low-power shutdown mode; (9)internal low-noise microphone bias, 2V; (10)available in the space-saving, 14-pin TDFN (3mm x 3mm)package; (11)-40°C to +85°C extended temperature range.

The absolute maximum ratings of MAX9814 are (1)VDD to GND:-0.3V to +6V; (2)all other pins to GND: -0.3V to (VDD + 0.3V); (3)output short-circuit duration: continuous; (4)continuous current (MICOUT, MICBIAS): ±100mA; (5)all other pins: ±20mA; (6)continuous power dissipation (TA = +70°C)14-pin TDFN-EP (derate 16.7mW/°C above +70°C): 1481.5mW; (7)operating temperature range: -40°C to +85°C; (8)junction temperature: +150°C; (9)lead temperature (soldering, 10s): +300°C; (10)bump temperature (soldering)reflow: +235°C.